Dell Inspiron 7791 2-in-1 Upgrade Guide

Lifecycle and support

A current model: sold new and supported.

Dates not listed haven't been published by the manufacturer or a reliable third party.

RAM (memory)

There are two DDR4 SO-DIMM slots (260-pin), both behind the base cover and both user-accessible. Nothing is soldered, so whatever is in there now can be removed.

What fits: standard DDR4, non-ECC, unbuffered modules at 1.2 V. Dell specifies 2666 MT/s (PC4-21300). 4 GB, 8 GB and 16 GB modules are all confirmed usable.

How much: Dell's validated maximum is 16 GB total - typically 2x 8 GB or a single 16 GB stick. Dell's own configuration table also shows 8 GB (2x 4 GB or 1x 8 GB) and 12 GB (8 GB + 4 GB). Some memory sellers list 16 GB modules as compatible, but no manufacturer source supports 32 GB in this laptop, so treat 2x 16 GB as unverified.

Speed: the platform runs memory at 2666 MT/s. DDR4-3200 SO-DIMMs are physically compatible and will simply downclock to 2666, so don't pay extra for them.

Watch out for: ECC or registered memory - neither is supported. And if you care about graphics performance, buy a matched pair (2x 8 GB rather than one 16 GB stick) to get dual-channel bandwidth, which the integrated UHD graphics benefits from.

Buying tips: DDR4-2666 (or 3200 if it is cheaper) 260-pin non-ECC SO-DIMMs; 2x 8 GB is the sweet spot and matches Dell's validated ceiling.

Buying tips

• DDR4 260-pin SO-DIMM, non-ECC, unbuffered, 1.2 V
• 2666 MT/s (PC4-21300); 3200 modules work but run at 2666
• 2x 8 GB for dual-channel - 16 GB total is the validated maximum

Storage

There are two storage bays and you can use both at once - a common setup is the NVMe drive for Windows and the 2.5-inch drive for bulk storage.

M.2 slot (1x): accepts both M.2 2230 and M.2 2280 NVMe (PCIe) drives. The slot runs at PCIe Gen 3 x4, roughly 3.5 GB/s, because the machine is Comet Lake-U. Gen 4 and Gen 5 NVMe drives physically fit but will run at Gen 3 speed, so don't pay the premium. Dell does not publish a capacity limit; 2 TB M.2 drives are widely reported working.

2.5-inch SATA bay (1x): one 2.5-inch hard drive or SSD on SATA III 6 Gb/s. Dell's service manual covers installing it alongside the M.2 drive. Dell does not state a capacity limit here either - a 2 TB 2.5-inch SATA SSD is confirmed working.

Watch out for: the mounting bracket, screws and flat SATA ribbon cable for the 2.5-inch bay are reported by owners to be stowed inside the chassis, so in theory a bare drive is all you need to buy. This is anecdotal, though, and may not apply to every configuration - open the laptop first and check before ordering spare brackets or cables. Drive thickness is not documented: a standard 7 mm drive should fit, but verify against the service manual before buying a 9.5 mm model.

One more thing: the card reader is microSD only. There is no full-size SD slot, no optical drive and no Ethernet port on this laptop, so plan your extras accordingly.

Buying tips: an M.2 2280 NVMe drive for speed, or a cheap 2.5-inch SATA SSD to fill the empty bay. Skip Gen 4/Gen 5 drives - the slot is Gen 3.

Buying tips

• M.2 2230 or M.2 2280, NVMe, PCIe Gen 3 - Gen 4/5 drives just run slower
• 2.5-inch SATA III (HDD or SSD) fits the second bay and can be used at the same time
• Open the case first to see whether the 2.5-inch bracket and cable are included

How to upgrade

Before you start

• Back up anything you care about before opening the laptop.
• Check your warranty terms - Dell documents these upgrades as user-serviceable, but opening the case may affect coverage.
• Read the exact model: this guide is for the Inspiron 7791 2-in-1, not the 7790.

Steps

1. Back up your data
   Copy important files somewhere safe before you touch any hardware.
2. Power off and unplug
   Shut the laptop down fully (not sleep or hibernate), unplug the charger and remove any connected devices or cards.
3. Ground yourself
   Work on a clean, non-static surface. Touch an unpainted metal surface or wear an anti-static strap so you do not damage the new part or the board.
4. Open the case
   Use Dell's service manual for the exact disassembly steps for your unit - screw counts and cover clips are model-specific and we would rather you follow Dell's instructions than guess. Owners report that the bracket, screws and SATA ribbon cable for the 2.5-inch bay are stored inside the chassis, so once the cover is off, look for them before buying spares.
5. Install the part
   Slide the SO-DIMM in at an angle and press it down until it clicks, or seat the M.2 / 2.5-inch drive in its bay and secure it. Do not force anything; if it resists, re-check the orientation.
6. Close the case
   Replace the cover and screws, and reconnect the charger.
7. Check the BIOS and firmware
   Power on and confirm in the BIOS that the new memory or drive is detected. Install any available BIOS or firmware updates from Dell afterwards if the part is not recognised.

Good to know

• Dell's documents do not confirm that the 2.5-inch mounting bracket and SATA cable are included in every unit; owner reports say they are stowed inside the chassis. Open the laptop before ordering spares.
• No documented thickness limit for the 2.5-inch bay: 7 mm drives should fit, but verify before buying a 9.5 mm model.
• No documented capacity limits on either storage bay; 2 TB M.2 and 2 TB 2.5-inch SATA SSDs are confirmed working by owners, larger drives are expected to work but are not formally validated.

Frequently asked questions

How much RAM can the Dell Inspiron 7791 2-in-1 take?

Dell validates up to 16 GB total across the two SO-DIMM slots - for example 2x 8 GB or a single 16 GB stick. Memory sellers also list 16 GB modules, but no manufacturer source supports 32 GB in this machine.

Does the Inspiron 7791 support 32 GB of RAM?

Not as far as any official source confirms. Dell's ceiling is 16 GB total. You may find community reports of more working on related Inspirons, but nothing backs it for this model, so buy with 16 GB as the working assumption.

Can I upgrade the CPU in the Inspiron 7791?

No. The processor is soldered (BGA 1528) and not replaceable - the i5-10210U and i7-10510U are the chips this laptop shipped with. The optional MX-class discrete GPU is soldered as well.

Can I use an M.2 SSD and a 2.5-inch drive at the same time?

Yes. The single M.2 2230/2280 NVMe slot and the 2.5-inch SATA III bay can both be populated at once - Dell's service manual covers installing both.

Does the Inspiron 7791 support Gen 4 or Gen 5 NVMe SSDs?

They physically fit in the M.2 slot, but the slot is PCIe Gen 3 x4 (around 3.5 GB/s), so a Gen 4 or Gen 5 drive will simply run at Gen 3 speed. Save your money and buy a Gen 3 drive.

Does this laptop have an SD card reader, optical drive or Ethernet port?

It has a microSD card reader only - not a full-size SD slot. There is no optical drive and no Ethernet port.

Official documents and references

• Dell Inspiron 17 7791 2-in-1 Service Manual (official disassembly and parts procedures)
  Primary source for exact disassembly steps
• Dell Inspiron 17 7791 2-in-1 Setup and Specifications - Memory (official memory configurations)
  Official RAM configurations and validated maximum
• Dell Community: Expanding storage on Inspiron 7791 (2.5-inch bracket and cable reports)
  Owner reports on the 2.5-inch mounting hardware
• Kingston Memory Shop: Dell Inspiron 17 7791 2-in-1 (compatible memory and drives)
  Third-party compatibility listing